Discount/Premium to nav is a figure that applies to closed ended stock funds, ie Investment Trusts (IT)
It describes how the trusts are trading relative to their Net Asset Value (NAV). A negative figure means a discount. A positive figure means a premium.
It is an important aspect to consider. As often these funds can deviate substantially from their net asset value. As an example, shares of ABC fund have a NAV (net asset value) of £5 per share, but the fund can be bought and sold for £4.90. This would mean the shares would be referred to as selling “2% discount to NAV”
It can be described as reflecting investors sentiment towards this Trust and the supply and demand patterns.
Hargraves Lansdown has an interesting video on this topic here: