Ajedrez means 'chess'. It's a fantastic and uncommon word to find in a romantic pop song, which makes it very memorable.
Alejandro Sanz uses it in a clever and beautiful metaphor: "Si tú eres mi reina, gano al ajedrez" (If you are my queen, I win at chess). He's comparing life and love to a game of chess, saying that having her as his 'queen' guarantees his victory in the game of life.
Bésame cuts right to the chase: Spanish singer Alejandro Sanz and Colombian pop star Shakira are completely done with overthinking. From the opening lines, the narrator refuses to leave love to chance, claiming that not even all the coffee in Colombia can wash away their crush's scent: "Ni con todo el café de Colombia me quito tu aroma" [Not even with all the coffee from Colombia do I get rid of your scent]. The whole track is a playful, direct demand to stop overcomplicating things and just kiss already: "No lo pienses tanto y bésame / Que se acaben los misterios" [Don't think so much and kiss me / Let the mysteries end].
There is great everyday Spanish slang tucked into these lines. When the singers belt "cero miedo, vamos enserio pa' adelante" [zero fear, we're going forward seriously], they shorten para to the spoken, casual "pa'". They also drop the blunt idiom "a quién le duela, que se aguante" [whoever it hurts, let them suck it up], basically telling outside critics to deal with it. The narrator even drafts a humorous to-do list where step one is urgent intimacy ("La primera es hacerte el amor con carácter urgente"), step two is staying forever, and step three is just repeating step one, but even more urgently. It is bold, fun, and makes no apologies for wanting full commitment right now.