nowadays you can get both types.
Working with old (leaded) stuff can be easier/more reliable for hobby projects, repair of old equipment and critical systems (telecoms, railway signals, industrial control) to the point you are still allowed to use it in Europe for commercial equipment in these applications).
Lead free solder needs higher bit temperature and can be harder to work with (my experience anyway)
If you are not working in a factory the risks aren't that bad.
I personally always use the old 60/40 leaded stuff, but that is because I am a bit older and am used to it 😉
You should if possible use a decent temperature controlled iron too (they are not as expensive as they used to be!) and its discouraged to mix up bits that have been used for leaded and lead free solder.
If you are new to soldering I'd suggest practicing on some less important circuits/components first and seeing what you get on best with..
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