what is replicated pine grain?

The short answer is its plastic with a picture and texture of wood grain, specifically pine wood. Usually furniture will be made of something cheap like particle board and covered with the replicated pine grain (laminate, vernier...etc) to make it look good. It gives a decent look for very cheap, but usually the piece of furniture is heavy (Cheap materials used like particle board are really heavy compared to real wood).

Ok, here is my "take" on your problem. It's hard without actually seeing your table. The lighter areas are less dense and therefore absorb more of the stain. That's the only thing that would cause the problem you are describing. Are you using an oil based stain or a water based? When we refinish furniture we use nothing but oil based stains because you do have more "control" over the penetration. So if you're using water based, get some good oil based stain. Do a test patch on a hidden area with the new stain. If you like it, great! If it's still doing the same thing, you need a seal coat to help stop the lighter wood from taking in too much stain. What we use when we get into that is a coat of tung oil. Formby's make a good, all tung oil and it's not terribly pricey. Watch the labels though, some so called tung oils actually have poly in them and you don't want that! Did I mention oil based stains and tung oil are MUCH easier to put on? You pretty much just rub them on with a soft lint free cloth, always going with the grain. No brush marks. And tung oil is a great finish all by itself too! Now it will take numerous coats to get a good seal on the wood but the result will be a nice, rich finish that can be repaired if you get a scratch or a ding! Can't do that with poly! My best suggestion is to sand the table with a 300, 320 grit sandpaper to really polish it up more than the 150. 150 is still fairly rough. The higher # sandpaper might just smooth things out enough to keep that from happening also. But I honestly think if you get some oil based stain you will be much happier with the results.

1

Here are literally thousands of organized woodworking projects in a members area and all you have to do is get them off your computer any time you want. Go here https://tr.im/FHG7W

There are thousands of plans so decide which one you are going to tackle next. The choice is yours to make so just click on the proper button for the specific project and then they are right there for you to pick one. The diagrams and instructions will be right there in the computer for you to access at any time or if you prefer you can print them out.