As the title says, I've recently stumbled upon the wikipedia article about the Blitz and I was suprised to find out that Hitler was initally opposed to the idea of 'terror bombings' that would target civilian buildings, mostly because he feared what the RAF would have done in retaliation. That changed after 24 August 1940, when some Luftwaffe elements drifted off course, and the bombs they dropped killed some civilians, which triggered an immediate British retaliaton with the RAF bombing Berlin. The German response to this is what is commonly known as "The Blitz". Is this correct?
Some followup questions: if he was afraid of retaliation, why didn't he try to reach an agreement with the British government (something like "okay sorry about that, how about we don't bomb your cities, you don't bomb ours")? Did he think the Luftwaffe was winning the Battle of Britain anyway? And if yes, why fear retaliation in the first place? And how was Hitler's policy regarding bombings in other countries (eg. France, Poland)?
I can't speak to Hitler's mindset, so I will be confining my answer to other portions of your question. You have the main narrative of the battle correctly though.
Did he think the Luftwaffe was winning the Battle of Britain anyway?
A recent post of mine addresses this issue. In brief, the Germans consistently underestimated British fighter production and numbers while the British consistently overestimated German aircraft production and numbers. This led to both sides misunderstanding the conflict as it unfolded. The Germans thought they were extremely close to winning and the British thought they were just barely holding on, while in reality the Luftwaffe was hemorrhaging planes and pilots at an unsustainable rate while the RAF was actually increasing in strength. From the very beginning the Battle of Britain was a battle of attrition that the British were winning.
I don't know that "fear" of retaliation is likely to be all that accurate. Anger at being bombed is much more likely. While the interwar bomber theorists (Wever in Germany along with Douhet, Mitchell, and Trenchard) asserted that bombing would be so terrible that civilian populations would rise up against their leadership and demand peace, the reality was that terror bombing was terrible for the targeted noncombatants but didn't actually create the effects that the theorists predicted.
And how was Hitler's policy regarding bombings in other countries (eg. France, Poland)?
Warsaw was bombed, including civilian areas. Rotterdam was also bombed. You could try to argue that these bombings were in support of ground operations (and some do), but I fall on the side that these and other Allied cities were bombed with at least a blatant disregard for civilian casualties.