Asset allocation refers to how a portfolio is allocated to various asset classes that have different historical investment returns and standard deviations. The simplest example is a stock-bond allocation, such as a 60% stock, 40% bond allocation, which is a common allocation for retirees. But there are dozens of more granular asset classes that can be managed as well, for example, U.S. large cap stocks or international small cap value stocks. Asset allocation is critical to effectively diversify your portfolio and reduce risk.
Asset location is different portfolio management strategy: one that few clients I meet have heard of. Few financial advisers implement it as well. Asset location seeks to minimize taxes by placing different asset classes in specific tax buckets (taxable, pre-tax, tax-free).