If you are married, your entire estate (including property) will be passed to your spouse up to a certain value. Anything over that value will be split between your spouse and your children or grandchildren.
If you are not married, your entire estate will be passed to your children unless you own your property as joint tenants, in which case your partner will inherit your share.
If you do not have children then things get passed on to your other family, starting with parents and then moving on to brothers and sisters then half-blood siblings.
Ultimately, you do not get to choose who gets what if you do not have a will in place so to make sure that the right things end up in the right hands you need a will in place.