Picture vs. Photo

A picture is any image regardless of how it was produced. A picture could be produced by drawing, painting, capturing an image by camera...etc.So we can say:

- He drew /painted/took a picture of sunset.
- Children drew pictures of their houses.

Picture is also an image seen on a television or cinema screen:

- We can't get a clear picture.

A photo also photograph(formal) is a picture made using a camera.

- We must take a photo.
- I took a lot of photos of the kids.
- wedding/holidays/passport/graduation photograph
So every photo is a picture, but not every picture is a photo.