Also is an adverb that means in addition; too.
Common usages of also:
1. Used to add extra information: "She's a talented musician and also a good painter."
2. Used to emphasize similarity: "I was also there that night."
3. In formal writing, often appears at the beginning of sentences: "Also, we need to consider the budget."
4. Can be used with "not only...but also" structure: "She is not only smart but also hardworking."