A double bond consists of a pi bond and a sigma bond?

A single bond between two carbon atoms consists of a sigma bond. (There are 2 carbon atoms sharing 2 electrons. They are tied together by a sigma bond). A double bond between two carbon atoms...

A sigma bond is a chemical bond which results from the end-on sideways overlap of two atomic orbitals to form a molecular orbital. Sigma bonds are formed by 'spin pairing electrons in any...

one pi and one sigma

If it is a double bond: Yes!, e.g. in H2C=O (formaldehyde, methanal) But in a single bond: No!, e.g. in H3C-O-H (methanol): Single bonds are sigma!

The central one is sigma bonding (s-s overlap) it is the strongest, the second is pi bonded (by 2p-2p overlap) and this is more loosely bound.