What Is This "core.xxxxx" Files

I found this files inside /home/user/public_html/forums

It's owner and group is nobody

When I try to cat and pico, all the weird thing came out

What is this files anyway? anybody can tell?

-rw------- 1 nobody nobody 25808896 Jul 9 00:06 core.9703
-rw------- 1 nobody nobody 25694208 Jul 11 11:56 core.9716
-rw------- 1 nobody nobody 25694208 Jul 11 11:56 core.9737
-rw------- 1 nobody nobody 25636864 Jul 10 01:34 core.975
-rw------- 1 nobody nobody 25870336 Jul 11 06:48 core.9758
-rw------- 1 nobody nobody 25694208 Jul 11 14:27 core.9763
-rw------- 1 nobody nobody 25632768 Jul 9 22:50 core.9786
-rw------- 1 nobody nobody 25944064 Jul 8 18:39 core.9799
-rw------- 1 nobody nobody 25870336 Jul 13 10:00 core.9802
-rw------- 1 nobody nobody 25632768 Jul 9 15:12 core.9806
-rw------- 1 nobody nobody 25694208 Jul 12 23:32 core.9809
-rw------- 1 nobody nobody 25870336 Jul 12 05:09 core.9815
-rw------- 1 nobody nobody 26005504 Jul 11 23:36 core.9816
-rw------- 1 nobody nobody 26005504 Jul 12 02:08 core.9826
-rw------- 1 nobody nobody 26005504 Jul 10 13:58 core.9833
-rw------- 1 nobody nobody 25632768 Jul 8 18:39 core.9854
-rw------- 1 nobody nobody 25632768 Jul 8 14:06 core.9865
-rw------- 1 nobody nobody 25694208 Jul 11 11:57 core.9881
-rw------- 1 nobody nobody 25870336 Jul 10 10:21 core.9901
-rw------- 1 nobody nobody 25694208 Jul 10 16:22 core.9903
-rw------- 1 nobody nobody 25694208 Jul 11 09:08 core.9913
-rw------- 1 nobody nobody 26005504 Jul 11 06:48 core.9922
-rw------- 1 nobody nobody 25632768 Jul 8 18:40 core.9927
-rw------- 1 nobody nobody 25870336 Jul 11 15:51 core.9942
-rw------- 1 nobody nobody 25694208 Jul 11 06:48 core.9946
-rw------- 1 nobody nobody 26005504 Jul 11 13:18 core.9983
-rw------- 1 nobody nobody 25944064 Jul 7 20:53 core.9989