What is the difference when the "4G" symbol and "o)))" symbol come up on my smartphone?

4G (sometimes labeled as LTE) is the type of cellular service your phone is connected to.  They show this on the display because you may be connecting to cellular service types other than 4G.  Usually there is a symbol associated with the signal strength of the cellular signal that is a series of four lines, the one on the far left being the shortest progressing to the longest one being on the far right.  This symbol indicates how "good" or "strong" the cellular service is at your current location.  If all the lines are "dark" than you have good signal strength, if some of the lines are grayed than you have less than ideal signal strength.

WiFi signal strength is universally displayed as a series of three or four curved lines that look sort of like a fan.  There is a very short line or dot at the bottom, a slightly longer line one above it and a yet a longer one above that.   The WiFi signal strength symbol works similar to cellular signal strength symbol. 

WiFi and cellular are two completely different technologies.  WiFi is intended to be used over very short distances, it's considered a "local area" network technology.  "Local area" means a defined space like a single building or single room in a building.  WiFi is not intended to cover areas larger than about 1000 square feet.

Cellular is a "wide area" technology, meaning it's intended to support large areas, areas measured in square miles vs square feet.  

Each has its advantages and disadvantages.  For WiFi it is much faster than cellular and generally speaking is "free" (where free is a relative term).  Cellular is what you pay for with the monthly smart phone contract.

4G is cell service, the other is Wifi you are connected to locally. 

It is telling you 4g data speeds are available on the cell tower