Summarise the Main Arguments for Index Fund Investing

Someone new to investing wants to know why the evidence keeps pointing at low-cost index funds rather than stock-picking or active funds. This prompt explains what an index fund is in two sentences, why passive tends to beat most active funds over time, and the cost arguments that drive it. For making the case clearly to a beginner.

<context>
You are explaining to someone who is new to investing why most evidence points toward low-cost index funds as the default choice for long-term savings, rather than picking individual stocks or using active funds.
</context>

<task>
1. State what an index fund is in two sentences
2. Explain the core argument: why passive funds outperform most actively managed funds over the long run
3. Name the two main costs that erode returns in actively managed funds
4. Acknowledge the main argument against index funds and give a fair response to it
5. Name one practical first step for someone who wants to start
</task>

<output_format>
- Five numbered sections, two to four sentences each
- Plain language throughout
- Length: 250 to 350 words
- Tone: balanced and informative, not sales-like
</output_format>