I have some of my savings in index funds. The low fees, the risk profile (if that's a proper term for it in English) and historical performance (which is not a guarantee for future performance) of certain indices is what I like about them.
If I create an index consisting of Company A, B, C, with 40% A, 30% B, 30% C and call that index "the sebcat index" others may sell sebcat index funds consisting of company A, B, and C stocks at those proportions. Of course, that's a bit too arbitrary. Normally you would have an index based on e.g., the N largest companies on a specific market/region. The index may be adjusted over time depending on market cap or something else, funds may not follow the index exactly, but that's the gist of it, to the best of my knowledge (see caveat). It's not in itself bound to geographical regions, though if you buy funds tracking foreign companies you should be aware of currency effects, politics &c (though local companies could be affected by that as well of course).
Look up a couple of indices (e.g., MSCI indices), then find what index funds on your exchange tracks these indices. Look up what the funds consist of exactly. If you compare two different funds tracking the same index, they should have similar performance over time. Buy one or two per index. The fees should be relatively small, 0-0.4%.
If you expect a crash to happen, or you see a crash happening that is not likely to end soon, sell any index funds affected and maybe put the money in interest funds, or gold, or something that you believe will not be as affected by, or benefit from the current situation on the market. Then buy back when (or if) the market goes up again (depending on your time frame).