Adult Social Care Glossary, v 0.6

Leave is often granted with a 'no public funds' condition and if that person uses or receives 'public funds' s/he breaks the terms of their leave and is no longer lawfully in the UK – although there are some limited exceptions where this rule is not applied. What counts as public funds is defined by the immigration rules and includes all the following housing-related benefits and services:

social security benefits
universal credit (or a legacy benefit)
housing benefit
housing services
a local authority tenancy
acceptance on the local authority housing register or waiting list
other benefits and payments
council tax reduction (council tax rebate/council tax support)
local welfare assistance (discretionary assistance fund/ Scottish welfare fund)

Most other non-contributory social security benefits also count, for a full list see the Home Office guidance. The law about public funds is in paragraph 6.2 of the immigration rules.