In Spanish, the structure of the verb change depending on the subject. Whereas in English there are no major variations on the way a verb is structured (other than the third person, adding the final –s → I eat, You eat, He/She eats), in Spanish we find that the ending part of the verb needs to change depending on the subject. When we talk about verb conjugation we refer to how a verb changes to show a different person, tense, number or mood. As an example, let’s see how the verb comer (to eat) changes as we change the subject (in the Present Tense)
Yo como zanahorias – I eat carrots
Tú comes manzanas – You eat apples
Ella come naranjas – She eats oranges
Nosotros comemos mucho – We eat a lot
Ustedes comen demasiado – You eat too much
Ellos comen despacio – They eat slowly
Notice how the root of the verb comer remains the same, «com–», and it’s the ending part the one that needs to change. In this example, I have shown you the present tense of the regular verb comer. In regular verbs, the pattern is going to be pretty much always the same (but every verb tense is going to have its own pattern). However, there are also a bunch of irregular verbs in which case there isn’t a particular pattern you can follow. In this cases, it’s more a matter of memorising and practising. Here is how you conjugate the irregular verb »ir» (to go).
Yo voy al cine – I go to the cinema
Tú vas al supermercado – You go to the supermarket
Él va a la estación de tren – He goes to the train station
Nosotros vamos mañana – We’ll go tomorrow
Ustedes van conmigo – You go with me
Ellas van tres veces a la semana – They go three times a week
Like I said, these patterns are going to be different in the past, future or conditional tenses but, for the purpose of this post, I hope you now understand what we mean when we talk about «conjugations».