Hi, everyone, i'm a beginner on houdi, i douwloaded the softeware since 1 week, and i don't know how to render animation. In first can we render animation in Avi or mp4 ? or we need to export them to an other software ?

No, you render as a sequence of individual image files. You will need another software to convert them to avi or mp4.

The image viewer application can export an image sequence as an AVI on windows. On MacOS and Linux there are other options. I generally use ffmpeg on the command line to convert to an mp4, but I admit it's argument syntax is a bit arcane and makes this process a bit of a chore. At least it's free.