La neta is popular Mexican slang for "the truth". It's an informal and authentic way to say "for real" or "honestly".
In this song, Ivan Cornejo sings, "Pero la neta te sigo extrañando" (But the truth is, I still miss you). Using this slang makes his confession of missing someone feel more raw and sincere, like he's sharing a secret straight from the heart. It's a perfect phrase to learn if you want to sound more like a native speaker!
This song is a straight-up heartbreak anthem. Ivan Cornejo lays out the feeling of being left behind after a relationship ends. He starts by remembering how great things were: "Enamorados empezamos" (We started out in love) and how he used to get "Mariposas... con tus abrazos" (Butterflies... with your hugs). But now, he feels like he's the only one left with those feelings, singing the painfully direct line, "Ahora soy el único amando" (Now I'm the only one loving).
He's completely stuck in the past, replaying memories of late-night calls when she'd say "que me amabas" (that you loved me). The whole time, he's wrestling with himself. He knows, "Yo sé que es malo para mí" (I know it's bad for me) to keep thinking about her, but he can't help it. He's just left wondering what happened and trying to figure out how to get her out of his head when the memories won't leave.