тоже is an adverb, it is used like "too". "Все кругом врут, и я тоже" "Everybody lies, me too."

также - can be used instead of тоже, but also is often used together with a union, where it can't be substituted by тоже: "иванов, петров, сидоров, а также кузннецов." Also it can start a sentence, while тоже can't (well, except there is an omited word): также пришёл Сидоров. Impossible to write "Тоже пришёл Сидоров".

Seems similar to the use of "too" and "also": "too" goes after a noun, "also" can go before.

I'm not a linguist. Maybe someone who can read a special vocabulary or a reference book, can give more accurate explanation.