What is LDAP used for?

That's a rather large question.

LDAP is a protocol for accessing a directory. A directory contains objects; generally those related to users, groups, computers, printers and so on; company structure information (although frankly you can extend it and store anything in there).

LDAP gives you query methods to add, update and remove objects within a directory (and a bunch more, but those are the central ones).

What LDAP does not do is provide a database; a database provides LDAP access to itself, not the other way around. It is much more than signup.

Well, there are LDAP servers and the LDAP protocol. Combined, it's a data store, or a database. It's not relational, but it's just a place to store data, and it's optimized to be efficient at reads more than writes. It doesn't support transactions.

Now, it happens to be very popular for storing credentials, but that's by no means its only purpose, and not its original purpose.

LDAP is the Lightweight Directory Access Protocol. Basically, it's a protocol used to access data from a database (or other source) and it's mostly suited for large numbers of queries and minimal updates (the sort of thing you would use for login information for example).

LDAP doesn't itself provide a database, just a means to query data in the database.

The main idea of LDAP is to keep in one place all the information of a user (contact details, login, password, permissions), so that it is easier to maintain by network administrators. For example you can:

• use the same login/passwd to login on an Intranet and on your local computer.
• give specific permissions to a group of user. For example some could access some specific page of your Intranet, or some specific directories on a shared drive.
• get all the contact details of the people in a company on Outlook for example.

To take the definitions the other mentioned earlier a bit further, how about this perspective...

LDAP is Lightweight Directory Access Protocol. DAP, is an X.500 notion, and in X.500 is VERY heavy weight! (It sort of requires a full 7 layer ISO network stack, which basically only IBM's SNA protocol ever realistically implemented).

There are many other approaches to DAP. Novell has one called NDAP (NCP Novell Core Protocols are the transport, and NDAP is how it reads the directory).

LDAP is just a very lightweight DAP, as the name suggests.

LDAP is also used to store your credentials in a network security system and retrieve it with your password and decrypted key giving you access to the services.

LDAP stands for Lightweight Directory Access Protocol (not a database). As the name says it is used for accessing/reading data. LDAP is a protocol to access data from directory servers which is a hierarchical database, it is designed for reading, browsing, searching, and organizing data. This kind of data we do not modify regularly or it is very infrequently modified data.

Big companies store their internal data, for example, user names with their title and id or phonebooks of their workers on LDAP servers (this server implements a tree-structured database). Those data can be reached by the workers of that company through the LDAP protocol. LDAP protocol runs over TCP or UDP protocol and accesses the server through port 389. There is also LDAPS that runs over SSL and accesses the server through port 636.