To be honest I never really had any formal classes that characterizes all angels in general, except for one long lecture on Bayyinah TV many years ago (if I'm not mistaken). And then Dr Omar Suleiman had a Ramadan series five years ago titled Angels in Your Presence, which we can watch for free on YouTube. We were taught some things in school but not in so much details.
Since believing in angels of Allah is one of the pillars of iman, it is our responsibility to get to know them better. This book is a good place to start, as the author explained systematically about the characters of angels, their attributes and abilities, their roles, how they worship Allah, and their relationship with other creations.
A lot of people question themselves, whether we are truly alone in this universe. As Muslims, we believe that we not only have Allah, we also have the unseen angels. Knowing their characteristics and their relationship with us makes us feel less lonely in this life, even when we are totally alone.
For example, they are with us when we attend gatherings of knolwedge and remembrance of Allah SWT, when we recite the Quran, or when we stand up to pray. They protect us when we ask for protection from Allah SWT.
They also send blessings to us for many reasons, such as teaching good things, eat pre-dawn meal before fasting, wait for payer in congregation, when we visit the sick, and when we send salawat upon Prophet Muhammad SAW.
What is the significance of them sending blessings on us? It is important because it has the effect of guiding us and bring us out of darkness into light.