Typically these are more greeting pleasentries that may or may not be formal (depending on the customs of greeting a politician from a country with formal protocal rules (like the Queen of England) or a nation with few protocals (I.E. The United States). If they don't do formal greetings, the greetings may be informal friendliness that is just water cooler talk (asking how the wife or husband is, how are your kids, great to see you again). Keep in mind that politicians are people too, and will often talk on a less formal matter about things that are not necessarily part of diplomacy that the people need to hear about.
Edit: If both politicians are politicians in the same country, again, it's probably pleasantries. Believe it or not, as partisan as some legislative bodies can get, it's not uncommon for a politician to have a friend from across the aisle who they may disagree with, but are still good buds. The United States Congress' gym is legendary for just how many deals get done while a Republican is spotting for a Democrat who is doing his bench presses.
A good example of such is discussed in "Yes, Prime Minister" episode "State Funeral" where the previous British Prime Minister's state funeral is described by the current Prime Minister as a way to discuss business with the visiting dignitaries. Morning a deceased politician was not the order of the day, and in fact, the Prime Minister had very little respect for the dead man to begin with. To put the issue aside, the big discussion prior to the funeral between two heads of Government is how to diplomatically tell the President of France that the gift of a puppy to the Queen is inappropriate because it wouldn't be Quarentined in time (meaning The President is either breaking the law in accepting or is being rude to France in refusing) and the proper seating order for the dignitaries (not alphabetical because that would mean sitting the dignitaries from Israel, Iraq, Iran, and Ireland next to each and this is a bad idea because Ireland "makes everything worse").