Some people learning Mandarin Chinese can get the words 跟 (gēn) and 也 (yě) confused, or use them incorrectly. The two words have related meanings and functions, but they're used quite differently.
跟 (gēn): "and", "with" (conjunction)
跟 is a conjunction. As with 和, you can't use 跟 to link verbs or verb phrases. This is an important point, and using 跟 or 和 to link verbs is a common mistake that people learning Mandarin often make.
Always remember that you can only use 跟 to link nouns together. That is, it links things not actions.
Have a look at some example sentences for 跟:
wǒ gēn wǒ nánpéngyǒu qù Běijīng de.
I went to Beijing with my boyfriend.
wǒ gēn wǒ bàba dōu shì lǎoshī.
My father and I are both teachers.
nǐ gēn nǐ de shìyou hédelái ma?
Do you get on well with your flat mates?
wǒ xǐhuan xué Zhōngguó de lìshǐ gēn wénxué.
I like studying Chinese history and literature.
As you can see, 跟 is simply used to link nouns together, where "with" or "and" might be used in English.
也 (yě): "also" (adverb)
也 is an adverb meaning "also", "too", "as well", "either" etc. Unlike 跟, it links verbs, verb phrases and adjectives. That's the most important difference between 跟 and 也.
Have a look at some example sentences for 也:
wǒ bàba shì lǎoshī, wǒ yěshì lǎoshī.
My father is a teacher; I am also a teacher.
wǒ qù wèn tā le, tā yě bù zhīdào zěnme bàn.
I went to ask her, and she didn't know what to do either.
tā yě hěn shuài.
He is also good-looking.
wǒ xǐhuan chǎofàn.
I like fried rice.
wǒ yě xǐhuan.
I like it too.
Notice how 也 always links verbs or adjectives, and 跟 always links nouns.