首先，also、as well、too 都有「也」的意思，大致有以下區別：
also 用在句中或句首，較常用於書面文本
Also 相較之下比較正式，常用於書面文本，一般放在句中或句首。放句中時常置於 be 動詞及助動詞後、一般動詞前。例如：
The guidebook has been published and is also available for download online.（這本指南已經出版，也可以在網上下載。） also 出現在 be 動詞後面
He is a famous pop singer who also writes poems and plays.（他是位知名流行歌手，也寫詩和劇本。） also 出現在一般動詞前
Frank Benjamin is the founder and also CEO of this company.（Frank Benjamin 是這間公司的創辦人，也是總裁。）
此外，also 也可以放在句首用以加強語氣。所以如果有句子是：
This documentary has gained wide attention and has also won several international awards.（這部紀錄片不只備受關注，也贏得一些國際獎項。）
我們也可以將 also 移到句首來加強語氣，寫成：
= This documentary has gained wide attention. Also, it has won several international awards.（這部紀錄片備受關注。此外，它也贏得一些國際獎項。）
as well 跟 too 通常用在句尾，而美式英文口語中更常用 too
As well 和 too 一般則用在句尾。在美式英文中，as well 又比 too 來得正式，一般口語中更習慣也更常用 too，但在英式英文中則沒有這個差別。我們來實際看幾個例子比較一下：
He’s a talented actor and also a popular columnist.（他是位才華洋溢的演員，也是位人氣專欄作家。） also 放句中；較常用於書面
也可以用 too 和 as well 改寫成：
= He’s a talented actor and a popular columnist too. too 放句尾；口語常用
= He’s a talented actor and a popular columnist as well. as well 放句尾；在美式英文中，as well 比 too 來得正式，口語上沒有 too 來得常用；在英式英文中則都常用
He played the electric guitar and also drums.（他彈電吉他也打鼓。） also 放句中；較常用於書面
也可以用 too 和 as well 改寫成：
= He played the electric guitar and drums too. too 放句尾；口語常用
= He played the electric guitar and drums as well. as well 放句尾；在美式英文中，as well 比 too 來得正式，口語上沒有 too 來得常用；在英式英文中則都常用文章來源: https://twgreatdaily.com/zh-cn/lmsFN3MBiuFnsJQV0utv.html