Questions about androids and tablets.. Please help?

3G/4G is the speed of the cellphone modem built in to the tablet.

The idea is that by building a data-only cell phone into the device you can use it to access the internet anywhere. 4G is about 4 times the speed of 3G.

To use this you need a data plan ($15-$30/month) and to be in an area covered by the signals. Most big cities will have good 3G coverage, 4G is only in a few places right now but growing. If there is no 4G in the area a 4G tablet will fall back to using 3G.

If this is for home use rather than on the road you don't want 3G or 4G.

Internet access at home is normally using wifi. This will be called WiFi (or sometimes 802.11) and may be followed by some combination of b, g or n, this is the speed of the wifi. n is better than g but it doesn't normally matter. All tablets will have some form of WiFi built in.

This does require that the person already has wireless internet at home, if they don't the tablet will be fairly useless.

Any tablet can be used as an eReader. Kindle is a free app for reading books from Amazon.com, there are lots of other ones around.

The card slot is a plug in socket for adding extra memory. It will normally be listed as an sd expansion slot, micro-sd slot or something similar. If it has one then it will take memory cards up to at least 16GB, probably 32GB.

Most have GPS. If the tablet doesn't have GPS then they will not be able to add it later with a GPS app. GPS requires a physical part in the tablet, if it's not there then there is nothing you can add later to give you GPS.

Gravity sensors have nothing to do with when you drop it, that will still break them. They let the tablet know which way up it is so that the screen can rotate to be the correct way up no matter how you hold it.

No one makes these in the USA, they are all made in the far east. You want one running Android 3.1 or higher, it should indicate that fairly clearly.

$70-$90 is unrealistic for what you have listed. The low end is closer to $300 with $400 being a good price for a well manufactured one.

The Asus Transformer is generally a good price for it's specification and build quality, it is currently $390 on amazon.com

In about 3 weeks time Amazon will release the Kindle Fire, it's sold as a e-reader but is a full Android tablet. That will undercut all the competition by a huge margin and cost $200. Don't confuse this with the Kindle, Kindle touch or Kindle keyboard priced $80-100, they are purely e-readers that can't do anything else. And yes, 4 different physical kindles and then a free kindle e-reader app for other tablets does make it a little confusing.

Where to shop: Well for the amazon one amazon.com is your best bet. For other makes amazon is still a good starting place, they may not always be the cheapest but they have reasonable customer service, sell most brands and will give you a good starting price.

http://www.google.com/prdhp? is good for price comparisons once you know a product name but isn't so good if you don't know what you want.

Generally you're going to get far better deals online than in a store but somewhere like best buy may be a good idea to get a better idea what you're looking at. Just don't feel pressured into buying something there.

3G refers to cellular service for Internet access. This provides access to the web when not near a WiFi hotspot but costs money monthly like a cell phone. All tablets have WiFi access to the Internet. All tablets will be able to run ereader apps. Most but not all tablets have an SD card port to expand memory and transfer files/media. GPS is a common feature and needed by mapping applications. Gravity sensor or accelerometer will help with automatically rotating the screen image when the user physically rotates the screen; it's also used in some games.

With the possible exception of the fire sale on HP TouchPads at $100 and the new Kindle Fires at $199, there are no tablet under $200 that I recommend. Here are some candidates that haven't held up to closer review:

M009S 2GB Google Android 2.2 Tablet PC: Despite 4ish star Amazon average, the 1-star comments are disconcerting:

http://www.amazon.co.uk/product-reviews/B004RAN7VI...

ePad: "Android ePad Tablet Reviewed. Verdict: Junk"

http://www.wired.com/gadgetlab/2010/08/android-epa...

Coby Kyros: "The bottom line: The Coby Kyros tablet offers a large screen for relatively little money, but it's a bad proposition at any price."

http://reviews.cnet.com/tablets/coby-kyros/4505-31...

Archos Arnova 10: "Its sluggish performance and unresponsive touchscreen make browsing the Web a real chore, though."

http://reviews.cnet.co.uk/ipad-and-tablets/archos-...

Ematic eGlide: "As of today [2011-04-04], I would strongly recommend against ANY Android 2.1 product."

http://www.amazon.com/review/RWVHZ9UXG14XP/ref=cm_...

SuperPAD / Flytouch: Unhappy users:

http://www.amazon.com/HDE-Flytouch-3-10-2-Super/pr...

Also, be careful of the fake clones:

http://androidforums.com/gome-flytouch-3/396917-p0...

It's generally not until the $199 (Kindle Fire or Lenovo Ideapad A1), $249 (Nook Color), $400 (ASUS Transformer), or $500+ (iPad 2, Galaxy Tab 10.1, Xoom, Toshiba Thrive, etc) ranges that you'll find tablets getting more respectable receptions by customers..