The secondary, tertiary and quaternary structure of proteins, the double helix of the DNA, the membrane structures and complex intracellular particles like the ribosomes are all maintained by weak interactions. The important thing here is the shape of the reactants. The more complementary the structures, the better their fit, the more weak interactions can form and the more stable is the resulting conformation or aggregate. This type of interaction is maybe the one most rightfully termed bond. They may develop considerable strength in non-water surroundings.
Water is an electrostatic solvent.
The electrons of a water molecule are distributed unevenly, since they are more strongly attracted by the oxygen atom than by the two hydrogens. Electronegative atoms, like oxygen, have a tendency towards polarity and supply the molecule with a directed dipole moment. Such an interaction is called a hydrogen bond. They are strongest, if the involved atoms are arranged linearly. The strength of their interactions drops drastically as soon as angles appear between the affected groups.