Short answer
Freehold generally means ownership of the property and land for an unlimited period. Leasehold generally means ownership for the length of a lease. The Title Register can usually show whether a registered property is freehold or leasehold.
Where tenure appears
For England and Wales property, the Title Register is normally the key written record for title information. It can include the registered tenure, title number, property description, proprietor details and other legal title entries.
Official source: https://www.gov.uk/get-information-about-property-and-land/search-the-register
Why tenure matters
Tenure can affect ownership, responsibilities, sale preparation, mortgage checks, ground rent, service charges, rights, restrictions and whether additional lease documents may be relevant.
Flats often have more than one title
A flat may have a leasehold title for the individual flat and a freehold title for the building or land. If both title options are shown for an address, the right choice depends on what you need to check.
What to order
If your main question is whether a property is freehold or leasehold, start with the Title Register. If you also need the general plan of the registered title, order the Title Plan as well.
Independent service note
LandRegistries.com explains document types and ordering routes. It does not provide legal, conveyancing or financial advice.