Ethylhexyl Methoxycinnamate

A clear, oil-soluble, "cosmetically-elegant" liquid that is the most commonly used chemical sunscreen.It absorbs UVB radiation (at wavelengths: 280-320 nm) with a peak protection at 310nm. 

It only protects against UVB and not UVA rays(the 320-400 nm range) – so always choose products that contain other sunscreens too. It is not very stableeither, when exposed to sunlight, it kind of breaks down and loses its effectiveness (not instantly, but over time - it loses 10% of its SPF protection ability within 35 mins). To make it more stable it can be - and should be - combined with other sunscreen agents to give stable and broad-spectrum protection (the new generation sunscreen agent, Tinosorb S is a particularly good one for that).

Regarding safety, there are alsosome concerns around Octinoxate. In vitro (made in the lab not on real people) and animal studies have shown that it may produce hormonal (estrogen-like) effects. Do not panic,the studies were not conducted under real life conditions on real human people, so it is probably over-cautious to avoid Octinoxate altogether. However, if you are pregnant or a small child (under 2 yrs. old), choose a physical (zinc oxide/titanium dioxide) or new-generation Tinosorb based sunscreen, just to be on the super-safe side. :) 

Overall, Ethylhexyl Methoxycinnamate is an old-school chemical sunscreen agent. There are plenty of better options for sun protection today, but it is considered "safe as used" (and sunscreens are pretty well regulated) and it is available worldwide (can be used up to 10% in the EU and up to 7.5% in the US).