At a beginning it was only for checking model and brand by using IMEI.
Now you can check a lot of info by using IMEI for LG, Motorola, Nokia, Microsoft, Sony and Huawei.
Huawei IMEI 86798102045xxxx Model NIN-A2 End of warranty 2017-01-24 Device model type mobile Country JP
Microsoft IMEI 35781606838xxxx Product code 059X0B8 Internal name RM-1073 Model Microsoft Lumia 640 LTE Network and country ATT US factory locked
LG IMEI 01409700124xxx Model LGV410 MSN 408CQLH124080 SUFIX TATTTN Production date 2014-08-14 Release date 2014-08-15 Device age 1 year(s) 11 month(s) 16 day(s) Location code N Network and country ATT ATT CSN LG0000660876747
Sony Warranty info Warranty ends;2016-12-28 3 UK (United Kingdom) Model;D2303 Marketing name;Xperia„ M2 Last seen;2016-08-14 17:32:50 Current version;18.3.C.0.37 New Software Update Available! Software available via OTA;18.3.1.C.1.17 Software available via cable;18.6.A.0.182 Software info Name;Lollipop Version;5.1 Release;2015-09 Status;Latest
Moderator warning: Sharing your IMEI number with anyone could possibly result in your device being cloned, blacklisted and other unfortunate outcomes. That's not to say there is anything wrong with this particular service, but please use services like this at your own risk.
p.s. to moderator, if this section is wrong, please move it to correct