Learn Finnish: Tyttö kävelee kaupan eteen. - The girl walks to the front of the shop.

It is in the genitive (possessive) case. Finnish postpositions like eteen (to the front of) usually require the word before them to be in the genitive case. Literally, this translates to "the shop's front". Also notice that adding the -n ending causes the strong double pp in kauppa to soften to a single p.

Does eteen simply mean "in front of"?

Not exactly, because Finnish is very specific about direction. Since the girl is moving towards the shop, we use eteen to mean "TO the front of". If she were already standing there not moving, you would use the static word edessä (in front of). Finnish location words change depending on whether you are going to, staying at, or coming from a place.

Where did the double L go when kävellä (to walk) became kävelee?

Kävellä belongs to a group of verbs that end in two consonants and a vowel (often called Type 3 verbs). To find the base stem so you can conjugate these verbs, the ending -llä drops off and becomes -le-, making the stem kävele-.

Why does kävelee end in a double E?