Phosphoinositide 3-kinases (PI3Ks), one of the families of eukaryotic enzymes was discovered more than 25 years ago and identified as a lipid kinase. PI3Ks can phosphorylate the 3-hydroxyl position of the inositol ring of phosphoinositides to generate lipid products and which involve in cell survival, growth, migration, apoptosis, proliferation, differentiation, intracellular trafficking and other cellular functions. In this review, the enzyme as a family comprising of 3 classes and 8 isoforms, the various domains found in the core structure of PI3K, the structural function of PI3K, its regulation and downstream targets were studied. It can be deduced that PI3K activity has a link with cancer and diabetes. It can be understood that PI3K pathway helps in the regulation of various cellular activities which leads to the protection of the immune system from malignant cells or pathogens, the pathway aids in the production of such malignant traits of the cancer cells and escape from immunity.