A rate "lock" or "commitment" is a promise from the lender to set a certain interest rate and a specific number of points for you for a specified period while your application is processed. This means your interest rate will not get higher while you are going through the application process.
Rate lock periods can be various lengths of time, between 15 to 60 days, with the longer ones typically costing more. A lender may agree to freeze an interest rate and points for a longer span of time, such as 60 days, but in exchange, the rate (and sometimes points) will be more than that of a rate lock of fewer days.
There are more ways to get a lower rate, besides going with a shorter rate lock period. The more the down payment, the lower your rate will be, since you will be starting with more equity. You can pay points to lower your rate over the term of the loan, meaning you pay more initially. To a lot of people, this makes sense and is a good deal..
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