To combine a series of images (PNG or JPEG) into a video, use the following. There is a more standard way to select the images by numbering them in a specific way, but the following makes it easier to work with wildcards without having to rename the images.
Example for creating a 30fps video with 5 images per second:
ffmpeg -framerate 5 -pattern_type glob -i '*.png' -c:v libx264 -r 30 output.mp4