@Laker
You can think of hydrogen bonding as an interaction between a hydrogen bond donor and a hydrogen bond acceptor. A hydrogen bond donor has a hydrogen bonded to an F, O, or N, and a hydrogen bond acceptor has a lone pair on an F, O, or N. In the hydrogen bond, the hydrogen from the donor interacts with the lone pair on the acceptor to form the hydrogen bond. Note: molecules can act as both hydrogen bond donors and acceptors.
For example, water can act as both a donor and acceptor since it has a lone pair (two actually) on the oxygen and two hydrogens bonded to an oxygen. In a mixture of water and formaldehyde, water can act as a donor and formaldehyde, because it has a lone pair on the carbonyl oxygen, can act as an acceptor. However, in a pure solution of formaldehyde, there will be no hydrogen bonds. Even though formaldehyde can act as a hydrogen bond acceptor, there are no hydrogen bond donors. In formaldehyde, the hydrogens are bonded to carbon and not one of the FON atoms required to make the molecule a hydrogen bond donor.
@geo
Salt bridges are common in protein-protein interactions (e.g. interactions between positively-charged and negatively-charged sidechains) and protein-protein interactions are a class of intermolecular interaction.