A moving element can hold in the same time numerous different motions which are all summed together. Think yourself having a bad hangover, every limb trembles uncontrollably say half an inch here and there. But you can still get up and walk to somewhere to get a remedy. Someone can filter out and see from your combined motion the trembling and thinks "thanks God, I'm not in that condition!"
The barman in the place where you finally enter notices the familiar customer coming in and says "Welcome again, nice weather today, how can I help you? The usual?" He ignores your trembling totally, he is interested in only that part of your quite complex motion that brings the paying customer in.
Different electromagnetic fields from different radio stations can cause to the same electrons in the same radio antenna several simultaneous movements (=currents) to different directions which all exist at the same time. The total current is the sum of the separate components. Cleverly designed circuits filter apart the wanted part generally based on the frequency.