Needles come in all shapes and sizes. Some are very specialized, depending on the task.
Sharps – General hand sewing, medium length, sharp point.
Betweens / Quilting - Shorter than sharps with small round eye for fine sewing.
Crewel / Embroidery – Larger eye for yarns and multiple threads, sharp point.
Self-Threading – Open slot at the top for dropping thread into eye without threading.
Beading – Very fine with a narrow eye to fit through beads.
Darning – Blunt tip and large eye for cloth repair.
Tapestry – Blunt tip, thick body and very large eye for heavy weight threads and yarns.
Upholstery – Large, long needles that are straight or curved for sewing very heavy fabrics, tufting and other upholstery work.
Soft Sculpture – Long needle for sculpting faces in soft sculpture dolls.
There are small tools called needle threaders that are very handy when threading the eye of a needle.
Put the wire end of the threader through the eye, put the thread in the middle of the threader wires and then pull the threader back through the eye. This will pull the thread right into the eye of the needle.
Many sewing machines have a threader hook on them that does the same thing.