This is the 858th most frequent Spanish word.
porque
"Porque" means "because" in English.
In this sentence, 'porque' is a conjunction introducing the reason for not going out (it was raining).
No salí a caminar porque estaba lloviendo.
I didn't go out for a walk because it was raining.
In this sentence, 'por qué' (written as two words) is used as a question phrase meaning 'why', introducing a question.
Me pregunto por qué no contestaste el teléfono.
I wonder why you didn't answer the phone.
In this sentence, 'porque' explains the cause or reason for the stated happiness (finding support in friends).