COBRA is not an insurance company; it is a federal law (Consolidated Omnibus Budget Reconciliation Act). It forces your old employer to let you stay on their health plan after you leave.
Why is COBRA so expensive?
When you were employed, your employer probably paid 70% to 80% of your insurance premium behind the scenes. Under COBRA, the employer stops paying. You now have to pay 100% of the premium, plus a 2% admin fee. That $150/mo plan you had? It might suddenly cost $800/mo.
Should you take it?
Avoid COBRA if you are healthy and just need basic coverage—buy an ACA Marketplace plan instead. You should only take COBRA if you have a massive ongoing medical issue (like cancer treatments or a pregnancy) and transitioning to a new network of doctors would interrupt your vital care.