LDAP stands for Light weight Directory Access Protocol. It is mature, well-defined, open and industry protocol accessing and maintaining the entries(user info) over internet protocol. It helps to add new, update and delete entries. It is mostly used authentication purpose. If you work in MNC you will have AD user account, this nothing but your LDAP user account.
More info, follow below link,
https://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol
For sharepoint integration, follow below links that may help you:
http://www.c-sharpcorner.com/uploadfile/Roji.Joy/sharepoint-form-authentication-using-ldap/
https://blogs.msdn.microsoft.com/spblog/2014/09/26/configure-a-sharepoint-2013-web-application-with-forms-based-authentication-with-a-ldap-membership-provider/