During save operations, Umbraco will generally take a database lock to avoid concurrency issues.
Access to this feature is via the IScope interface, for example:
using(var scope = _scopeProvider.CreateScope())
// Carry out save operation.
Each lockable entity is represented by an integer Id, stored along with the state of the lock in the umbracoLock database table.
Packages or custom solutions working with custom data via the IScope interface can introduce their own records to this table. However it's important to not clash with either core identifiers or those introduced by other packages.
A reference is maintained here of known identifiers: