Do we need to carry photos for passport?

You need to supply photos when you apply for a British passport, as the passport application form tells you. In other countries you will have to look at their forms, but in general photos are needed.

Yes

You don't need to carry additional photos with you other than thee one that is in the passport.

Your question makes little to no sense.

Your passport contains a photograph of you.

If you are carrying your passport (for identification and/or international travel) you are already carrying the photo.

What on earth does that mean? There's a photo IN your passport.

Where did you get that idea?

When you apply for a passport, you enclose passport sized photos with the application and other documents, One photo is welded into the information page in the passport.