Tener, to have, is a very useful verb and is unsurprisingly one of the first ones we learned despite its irregular conjugation. When you are stuck talking in the present tense with a limited vocabulary the conversation naturally turns towards describing yourself—I have a sister, I don’t have a cat—clear uses of tener. If you are bold you may even venture a, “do you have a pen?” to which your partner may not respond, being that there are three words for pen and you probably each remember different ones (esfero, boligrapho, and the not-used-here-but-still-in-the-textbook pluma).
Less obvious uses of tener include feelings: it’s not “I am hungry,” it’s “I have hunger,” not “I am lazy” but “I have laziness,” like it’s a disease (debatable, yes). I think this has to do with the transient nature of these feelings. The verb “ser,” or “to be”, is used generally for fairly permanent things: “I am from the US,” “She is a gardener” ect. The other slightly similar verb “estar” is also like “to be” but for location: “the cat is on the table,” “Paris is in France.” Three verbs for the price of one, and a little odd coming from English but easily graspable.
So now that I have armed you with this new word you are free to construct various sentences with the octopus (18pus?) above and barrage the world with your complaints: “tengo sed…” “tengo frio…” “tengo hipo…”
(I’m thirsty, I’m cold, I have the hiccups. note: tengo is only for talking about yourself, in the present tense)