Tener vs Haber

Tener is used to show possession

Tengo un lápiz [I have a pencil]

Haber Is used mainly as an auxiliary verb in tenses like the present perfect [haber + past participle] (i.e. I have been).

He estado aquí antes. [I‘ve been here before]

It’s also used impersonally to say “there is/are” with hay (never followed by nouns proceded by definite articles [el/los/la/las)

Hay un lápiz sobre la mesa [there’s a pencil on the table]

Había manzanas en la cocina [there were apples in the kitchen]