The regular pronouns, yo, tú, él, ella, usted, ellos, ellas, and ustedes, are used with a conjugated verb. Once you get more familiar with the language you can drop the pronoun and just use the verb. Because the conjugated verb can only go with certain pronouns the verb tells us what the pronoun would be. Yo pago means I pay (or I'm paying) but so does pago by itself. If you want to say I'm paying you it's Yo te pago or just te pago. You pay me would be me pagas. The verb tells us who's doing the action and the indirect pronoun tells who the action is being done to.