Hablo means "I speak" in Spanish. It can only be used when talking about yourself. The infinitive (basic form of a verb) for hablo is hablar. If you're talking about what he/she speaks, you say habla. If you're talking about what whoever you're talking to speaks, you say hablas.
But hablo means "I speak". For example, "Hablo español". Which means "I speak Spanish". (You could also add a yo before the hablo so it says "yo hablo español" but you don't need to)