"لو"
Often comes with events that are impossible or hard to happen, e.g.
"لو كان لي جناحان، لما بقيت علي الأرض"
“If I had wings, I wouldn’t stay on the ground”
Also, it could be used to regret something in the past, e.g.
لو ذاكرتُ جيداً، لحصلت علي درجات أفضل
“If I had studied well, I would have got better grades”
"إذا"
Is used with events or conditions that are most probably gonna happen, e.g.
إذا مات أبي، ادفنوه في بيته
“If my dad died, bury him in his home”
إذا تأخرَ صديقي، حتماً سأنتظره
"If my friend comes late, definitely I will wait for him”
There’s also another word with the same meaning “if” but different usage called
"ْإن"
This one is used with events that may happen but not for sure, e.g.
"إنْ جاء أبي، فلا تخبره بمكاني"
“If my dad comes, don’t tell him where I am”