Direct ISA is just a provider's term for an ISA that, generally, you can only access / manage by phone or online
Read this from National Savings and Investments:
Mini ISAs
There are two types of mini ISA:
cash (maximum investment �3,000 per tax year)
stocks and shares (maximum investment �4,000 per tax year)
You can invest in one mini ISA of each type in the same tax year, and each one can be with a different provider. NS&I offers two cash ISAs � the NS&I Direct ISA and the NS&I cash mini ISA. You can only invest in one of them each tax year. We do not offer a stocks and shares mini ISA.
Maxi ISAs
Or you can invest up to �7,000 per tax year in a maxi ISA, which must contain stocks and shares. It can either be made up entirely of stocks and shares, or a mixture of cash and stocks and shares.
If your maxi ISA contains a mixture of both, the investment limit for the cash part is �3,000 per tax year. NS&I does not offer maxi ISAs.
The rules for investing in ISAs
The total amount you can invest in ISAs in a tax year is �7,000. This can either be in one maxi ISA or two mini ISAs.
You can only invest in one cash mini ISA in each tax year � up to a maximum of �3,000. If you invest in a cash mini ISA you cannot invest in a maxi ISA during the same tax year. This will limit the amount you can invest in stocks and shares through ISAs to �4,000 in that tax year.