Changes to the database schema are called migrations, what are data changes called?
Check out DML - Data Manipulation Language. This includes CRUD operations (Create (i.e. INSERT - not to be confused with the CREATE TABLE statement below), Read (i.e. SELECT), Update, Delete) on Tables. It's what people associate most classically with SQL.

Compare this with DDL - Data Definition Language. DDL involves the CREATE TABLE and ALTER TABLE operations (among others - related to INDEXes amongst other things).

For completeness, there is also DCL - Data Control Language. DCL is for the control of access to tables - GRANT and REVOKE (i.e. GRANT READ ON schema_name.table_name TO user_name.

The SQL standard is an attempt to homogenise DML among various vendors - its success has been limited so far. Many servers implement non-standard extensions, their own Stored Procedure language, DDL and DCL. Take a look at the "Procedural extensions" section on the SQL page above.

Changes to a schema (from the same version of the same server to another or even within the same instance) are simply called DDL - CREATE TABLE, ALTER TABLE, DROP TABLE.

Changes to a schema brought about (normally) by an upgrade (e.g. Oracle 9 to Oracle 11) are called migrations - going the other way is called either downgrading or backward migration.

Changes to a schema due to a change of server (i.e. Oracle to SQL Server) are called ports ("porting"). These are normally quite difficult and involved due to the differences between servers mentioned above.