I suppose you refer to this sentence ""Θέλω να περπατήσω." "https://forum.duolingo.com/comment/22425852).
περπατώ is a continuous form used in the present tense and the future continuous and continuous present subjunctive:
περπατώ (I walk/ I am walking)
θα περπατώ (I will be walking)
θέλω να περπατώ (I want to be walking)
περπατήσω is the non-continuous form used in the simple future tense and the non continuous subjunctive:
εγώ θα περπατήσω (I will walk)
εγώ θέλω να περπατήσω (I want to walk)
Wiktionary often has conjugation tables. Here is the one for περπατώ.