It is both.
Walk is a regular verb so the past and the past participle is walked. This is true for all regular verbs.
Past is : Beat (itself) Past Particle : Beaten
The simple past and past participle is had.
"Encouraged" is the simple past and past participle of the verb "encourage".
The past participle for shrink is shrunk.shrink / shrank / shrunk
The past participle of do is 'done'.
The past participle is burst.
The past participle is drawn.
Been
The past participle (and simple past) is loved.
The past tense is took. The past participle is taken.
infinitive: be past: was/were past participle: been
The past participle of "hide" is "hidden".