Relational Databases organize data into tables with rows and columns. They use Structured Query Language (SQL) for defining and manipulating data. Examples include MySQL, PostgreSQL, Oracle, and SQL Server.

NoSQL Databases provide a mechanism for storage and retrieval of data that is modeled differently than relational databases. They are designed for distributed data stores and can handle large volumes of unstructured data. Types include document stores, key-value stores, column-family stores, and graph databases.

Database Normalization is the process of organizing data to reduce redundancy and improve data integrity. It involves dividing large tables into smaller ones and defining relationships between them.

ACID properties (Atomicity, Consistency, Isolation, Durability) are a set of properties that guarantee reliable processing of database transactions. These properties ensure data validity despite errors, power failures, or other mishaps.

Database Indexing is a data structure technique used to quickly locate and access data in a database. Indexes are created on columns to speed up search queries, though they require additional storage space and can slow down write operations.