In this example question, it says identify the type of functional group or groups present within the following compound. So here we have a bunch of carbons and hydrogens, so we know that it's a hydrocarbon. Now let's lookout for double bonds and triple bonds because those seem to be big indicators of the different types of hydrocarbons that exist.
If we take a look here, we have these two carbons double bonded to one another. These two carbons double bonded to one another and then here these two carbons triple bonded to one another. Now remember if you have a triple bond between carbons, that represents an alkyne functional group and then here these two double bonded carbon groups represent alkene functional groups.
This structure cannot be seen as an alkane because an alkane possesses only single bonded carbons and hydrogens together. So we wouldn't count that as a unique functional group for this compound. So again, look out for the double bond. Look out for the triple bond. Those are good landmarks to look for when looking at different types of hydrocarbons within any given compound.