An integral membrane protein is a kind of membrane protein, which is perpetually combined with the biological membrane. All transmembrane proteins are integral membrane proteins, but not all integral membrane protein are transmembrane proteins.
These proteins are anchored in the lipid bilayers and only non-polar, hydrophobic amino acid residues would be found in the part of the protein, which crosses the membrane. In the interior of the bilayer, these residues would be hidden from the water solvent and associate with the non-polar lipid tails.