話せます and 話します
What is the difference?
Well, for starters, both are different inflections of the verb 話す, which means "To speak". The first one you typed, 話せます, is the potential form with polite ending, meaning " can speak". The second one, 話します, is exactly the same as 話す ("To speak"), only using the polite ending ~ます.
- I speak Japanese. = 私は日本語を話す (standard)
- I speak Japanese. = 私は日本語を話します (polite ending)
- I can speak Japanese. = 私は日本語を話せます (potential form, polite ending)
Also, the potential form without using the polite ending would be 話せる。
- I can speak Japanese. = 私は日本語を話せる (potential form, no polite ending)
話ます does not exist.
話す is the dictionary form of the verb and the ending す is the part that conjugates to し when in polite form.
You can only add ます directly after the kanji if the dictionary form of the verb ends in an "iru/eru" sound such as 寝る 'neru' sleep which becomes 寝ます nemasu
If the question was related to ability you were probably marked wrong for writing 話します because the sentence required the potential form of the verb 話せます・話せる
Either that or it was along the lines of "we will have a talk" where 話 was actually being used as a noun pronounced "hanashi" and combined with the verb する・します "to do". As a noun is the only time 話 uses "shi" is part of the actual reading.
話をします - to do talking, to have a talk