みたいな is the attributive (pre-noun) form of みたいだ, meaning 'like' or 'similar to'. You use it to describe a noun by comparing it to another noun. For example, 東京みたいな町 means 'a town like Tokyo'. It's more casual and conversational than のような.

You can also use it after a verb or adjective in plain form, like 夢を見ているみたいな気分 (a feeling like I'm dreaming), but at N4 you'll mostly see it after nouns. When you use it, the noun that follows is what you're describing. The comparison noun before みたいな is the thing you're comparing to.

Be careful: みたいな must come before a noun. If you end the sentence, you use みたいだ or みたい (casual). So 'It's like Tokyo' is 東京みたい, not 東京みたいな.