Hi, intrusions are malicious/harmful requests coming to your website.
HMWP IDS detects such malicious requests and notify you about it. But all these requests might not be harmful and you need not worry as HMWP IDS will take care of this and will block the malicious requests if Impact level is more than 20 (default value specified in HMWP IDS). You can stop receiving emails regarding this by setting “Notification Threshold” option to 0 in IDS Firewall tab.

Note: If in case, valid request is also listed as intrusion then hover over that request name and click on Exclude link to add it to exception list.