Asset class allocation mean what type of asset you are investing in. There are 3 main classes (the classic view of investments): Equity, Fixed Rent, and Money Market instruments (short-term investments that generate interests, loans to be simple). However, there is a forth class, Alternative Investments.
Alternative investments as a class have appeared because of their different risk characteristics and the increased exposure of investors over time on this type of assets. Alternative investments include Real Estate, Commodities, Derivatives, Artwork & Collection pieces, etc. By 2014 25% of the world investment portfolio was on alternative investments.
You can classify your investments in the classic way, or in the “new” one, it is up to you. I would use the latter.
Just remember that alternative investments can take other forms. For example, you can buy an equity share of a company that only trades commodities as its core business, so call it an alternative investment, not just equity. If you buy a house with the intention to resell or rent it, you have an alternative investment. If you buy a REIT share in NYSE, you also have an alternative investment, it doesn’t matter if you own 0.02% of the REIT.
Hope this helps.