These words are all used to show similarity or sameness:
Jeff plays soccer. Greg plays soccer, too.
Jeff plays soccer. Greg also plays soccer.
Jeff plays soccer. Greg plays soccer as well.
The only difference is in their placement in the sentence. Too and as well are used at the end of a sentence. (As well is more formal than too). Also usually goes before the verb or adjective.
He likes chocolate.
I also like chocolate.
I like chocolate also.
I like chocolate, too.
I like chocolate as well.
The apples are delicious.
The pears are also delicious.
The pears are delicious also.
The pears are delicious, too.
The pears are delicious as well.
The expression as well as can be used in the middle of the sentence, and is similar to "and" or "not only... but also":
She bought the necklace. She bought the earrings.
She bought the necklace and the earrings.
She bought the necklace as well as the earrings.
She bought not only the necklace, but also the earrings.
You can also rephrase this to use also, too, or as well:
She bought the necklace. She also bought the earrings.
She bought the necklace. She bought the earrings, too.
She bought the necklace. She bought the earrings as well.
As you can see, there are many correct ways to say the same thing!