It means “here you go” or “please”. In a good way. But you also use it at the end of a sentence in an debate if you’re angry just to emphasize again what you said. You also use it agree on something, like “right” in english. It is used in different occasions and the actual meaning changes a little, you can see it a lot in movies.
A lot of things... •To show something special (~here is.. ) "Voilà la Tour Eiffel!" - "Voilà ma cousine Danielle" • As a conclusion, to resume an evident thing, after a story for example "Et voilà comment elle est partie." - "Elle n'avait pas assez de sous pour payer le train... alors voilà" • to affirm, confirm something, as a "that's it" "oui voilà! c'est ce que je pensais" • an expression : "Voilà tout" ~ "that's all"- used after a short explaination for an obvious thing :)