The first image shown at the left hand side is a pi bond. The other two images show sigma bonds.
In chemistry, a bond results from the overlap of atomic orbitals. This overlap may be end to end (sigma bond) or side by side (pi bond). Having said this, it is easier to decide whether the bonds in the image shown are sigma or bi bonds.
If we label the images; 1,2,3 from left to right, we can see that the overlap in image 1 is side by side. The electron density lies above and below the plane of the bond. This is a pi bond. In images 2 and 3, the overlap occurs in an end to end manner. This is a sigma bond.
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