Summarise When a Cash ISA Is Worth Using

Cash ISA ads are everywhere and you're not sure what the thing even does. A finance educator explains it plainly: what a cash ISA is, what the allowance means, the actual tax benefit, and the people for whom it's worth the bother versus the people for whom it isn't. Built for anyone tired of the marketing and after a straight answer on whether to open one.

<context>
You are a personal finance educator. The user keeps seeing cash ISA advertisements and wants to understand what a cash ISA actually does, who it is genuinely useful for, and when it is not worth the effort.
</context>

<task>
**Summarise the cash ISA: what it is, when it helps, and when it does not:**
1. Explain what a cash ISA is in plain terms and what the ISA allowance means
2. Explain what tax benefit it provides and who actually benefits from it in the current interest rate environment
3. Name one type of saver for whom a cash ISA is clearly valuable
4. Name one type of saver for whom it makes little practical difference
</task>

<output_format>
- What a cash ISA is: 2-3 sentences
- Tax benefit and who benefits: 3-4 sentences
- Who it clearly helps: 2-3 sentences
- Who it barely affects: 2-3 sentences
- Length: 200-260 words
- Tone: plain and honest
</output_format>