There are two main types of large funding available to charities. These are funding from statutory grant makers and funding from charitable trusts or foundations.
The two main differences between a grant maker and a trust fund are that grant makers will normally only give funding to projects and will be specific in the way that the money given can be spent. They will also require evidence and proof of receipts/accounts.
Trust funds will generally give an amount of money which is unrestricted (unless otherwise specified); whereas grant makers will normally specify what you can spend the money on.
Depending on the size of the trust, you would normally expect to receive smaller amounts of money than if you were applying to a specific grant maker. However, you are more likely to receive money that you could spend in any way to benefit the charity. So the avenue you pursue primarily depends on what you need the money for.