According to my dicctionary, it means 「〜時はいつも / 〜するといつも」like "when I ..., I always~". Whenever I talk with my friend I feel glad. --> 私は友だちと話すときいつもうれしいです。 I would say: 友だちと話すといつもうれしくなります。 (En español, sería "siempre que hablo con mi(s) amigo(s), me alegro / estoy feliz".) Ex.) You can call me whenever you like. (あなたが電話したい時に、あなたはいつでも私に電話してもいいです --> more natural: いつでも電話してください。) I hope this helps you.

と, as well as meaning "and", has another use as a conditional particle, similar to the 〜たら and 〜えば verb endings. For example: 教科書を読むと、眠くなります。 When(ever) I read my textbook, I become tired.

と is a conditional particle, corresponding rather closely to English "if". "Whenever" is a bit too strong, and "when" is too weak for its meaning. It is a simple conditional, meaning "if A, then B follows" without the emphasis of "Whenever". 私は友だちと話すときうれしくなる -> When I talk with my friend, I feel happy. 私は友だちと話すとうれしくなる -> If I talk with my friend, I feel happy. 私は友だちと話すといつもうれしくなる -> If I talk with my friend, I always feel happy.