All property and income of either spouse / partner is either marital / civil partnership or non-marital / non-civil partnership. The law has very different treatment to each category of assets. The law (unhelpfully) does not give a definite definition of either category.
Marital/civil partnership property includes resources acquired by either spouse/partner during the marriage/civil partnership and sometimes during pre-marriage/pre-civil partnership cohabitation when cohabitation has moved seamlessly into a marriage/civil partnership. It may include inflation or other growth on non-marital/non-civil partnership assets. It may often include the family home even if owned by one spouse/partner before the relationship. It will include non-marital/non-civil partnership assets which have been mixed and mingled with marital assets or used for family purposes. It does not matter if only one spouse/partner acquired it if, for example, the other was doing other work or looking after the home or children. It is all that was acquired during the relationship.
Working out the nature and source of the assets is crucially important in law for the financial settlement upon divorce/dissolution. If you have any doubt you should take legal advice.
Non-marital / non-civil partnership property includes any assets acquired prior to the marriage/civil partnership (and sometimes before pre-marriage/pre-civil partnership cohabitation), inherited and gifted resources and some resources which distinctively accrue after separation. Sometimes it may not include the growth in the value of non-marital / non-civil partnership property through inflation etc. Quite often it may not include the family home even if purchased with non-marital/non-civil partnership funds.
Working out which assets are non-marital/non-civil partnership is crucially important in law for the financial settlement upon divorce/dissolution. The law treats each category of assets very differently. If in doubt, legal advice should be taken.