What is a difference of opinion? Can it be measured and or shared?

There are many aspects of Islam which are open to interpretation based on various sources and proofs, thus resulting in differences of opinion. Note that within Sunni Islam there is no difference of opinion on the fundamentals of our deen (i.e., Tawhid, Risalah, 5 pillars, etc.). There is difference of opinion on many minor things, like the details on how exactly to pray the Salah, or the rulings on certain Fiqh (jurisprudence) issues. Some opinions hold more merit than others, due to stronger proofs or reasoning. People choose to follow opinions based on a variety of factors, including what they were raised on, what their society (family, friends, and community) follows, or maybe based on their own discretion after evaluating the various opinions, or simply because it's the only opinion that they are aware of.