Spider Veins
Most common, mildest form of disease consisting of very tiny dilated veins within the upper-most layers of the skin. They may be blue in color and look like lines on a road map, or they may appear as red-purple starburst clusters. They tend to fan out on the outside of the thigh, around the ankles or behind the knee.
Reticular Veins
Somewhat larger/deeper veins that form branching networks that are sometimes lacy in appearance. These often underlie a spider vein network. The only way to eradicate the spiders is to treat the largest vessels first.
Varicose Veins
These are markedly enlarged veins that bulge, appear twisted, are sometimes painful, and may even be prone to blood clots. These are “true” varicose veins.
Chronic Venous Insufficiency (CVI)
This term refers to an advanced stage of venous disease, usually as the long term sequela of ongoing venous hypertension from venous reflux from valvular incompetence or as a consequence of prior blood clots (postphlebitic syndrome).
CVI usually manifests as severe pain, swelling, skin changes (thickening, swelling pigmentation changes), and in its most advanced stages, skin breakdown and ulceration. Symptoms can be severely disabling, and occasionally limb-threatening.
If the superficial veins are the source of the problem, sclerotherapy, microphlebectomy and endovenous laser ablation, or a combination of these therapies, may eradicate the causative reflux. If the deep veins are the problem, more limited therapeutic options are available. Most often patients are treated with lifelong compression stockings. There are some promising surgical techniques for potentially correcting this problem. However, centers and physicians providing these services are extremely rare, with only a few places in the country offering such treatments.
Venous Ulcers
This is most severe consequence of chronic venous insufficiency (CVI). 
Once the ulcers form, they can be very difficult to treat, particularly in patients who also have a history of diabetes or poor arterial flow in the legs. Intensive treatment with special dressings, bandages and stockings are often required for healing. Wound care specialists are sometimes involved in the management along with your primary physician.
As noted previously, correction of the underlying venous abnormality, using sclerotherapy, microphlebectomy and/or endovenous laser ablation, is often necessary for adequate healing and to help prevent recurrences. Nonetheless, continued use of the compression garment is almost universally advised.
Your physician will decide which compression garment is appropriate for you.