Weird sensation in my legs?

So I found a way to get this really good and weird sensation in my legs and I can't explain it. If I try to go really far with it it centers towards my crotch area. Now that I did It I see that I can make upper body feel it just a little but it's extremely intense in my legs I can do it on command. Could anyone explain to me what it is.(This is legit)-first question asked on here.