My own notes on the basics of SQL
SQL - Structured Query Language is a programming language that lets you create, change, and pull information from, relational databases. It differs from many programming languages in that it deals less with algebraic and algorithmic actions, and deals more with declaring sets, and retreiving information based on type.
RDB - A relational database is a system of storing information that logs data into one or more tables, made of columns and rows. Each row of these tables will represent a unique individuals information, while each column while describe an attribute of each individual. Often tiems relational databses employ integrity rules to make sure that the data stored within them is consistent and correct. This could mean rules like each individual must have their own unique, id number to identify them (a primary key), or that only one user at a time can change a certain row's data.
RDBMS - A Relational Database Management System allows users to create, and maintain their own databases. Common among hobbyists and startups are free, open source RDBMS like MySQL, SQLlite, and PostgreSQL. However large organizations usually opt for third party, vendor supplied versions of SQL, which are mroe secure and can scale more easily. They will pay companies like Microsoft, and Oracle for their enterprise SQL solutions.
GUI Tool - A GUI (Graphical User Interface) tool is a program that lets you use SQL outside of the command line. After you have downloaded a RDBMS like PostgreSQL you have a fully operational databse which you can run fully from the command line. A GUI tool however allows you to use the same database in a custome SQL program, thats much more visually appealling. An example of a GUI tool would be p sequel.