The deceased person’s “estate” is all their property, including their personal possessions (like clothes and jewellery), money in bank accounts, any house or other land they own (called “real” property), proceeds from insurance policies, and shares in companies.
The deceased’s estate won’t include any property that he or she owned jointly with a partner, like a house. Because they owned the property jointly (legally, this is called owning as “joint tenants”), this means that when one of them dies the other becomes the sole owner. (This is different from owning property together as “tenants in common”, which is where you each have a separate ownership share that you can pass on under your will to whoever you choose. And note that although these technical legal terms refer to “tenants”, in fact they’re about ownership, not about renting or leasing property.)