how do you understand "Customer is always right" ?

I understand it that the customer even if he was wrong I must give him the feeling that he is right and try to fix his problem by explaining the right thing so I mustn't tell him that you are wrong but I will ask him what he really want from he product and how he uses it and from his own mouth I make him tell the wrong thing he did and by this way he will know that he was wrong but he will fell i didn't saw what he did and that's how i give him the feeling that he is right all the time

"The customer is always right" means that, in service professions, whatever the end user wants, the end user gets. In a restaurant situation, for example, if the customer wants to substitute bananas for strawberries and egg whites for whole eggs, you (the cook) must comply with this request. Otherwise, the customer will leave without paying and/or never return to the restaurant.

عندما نقتنع كل الاقتناع بان العميل هو سبب رزقى واعتلائى لمناصب اعلى فانه حقا على حق

Bottom line: The customer brings business & money to your company.
Now in case the customer is insisting for an unjustified demand, it is up to your diplomatic, negotiation & customer communication skills that how do you manage to accommodate her/his demands, while at the same time keeping you (or your company) at safer side.

I understand mutual systems that makes both "customer and supplier" satisfied all the time but:
1- If the customer is bigger than the supplier; the customer rules and in case the customer mistakes, surely they will confess and compromise.

2- The supplier bigger than the customer; in this case of course the supplier's policies rules.
But again there is should be mutual policy with "give and take" points depending on the size of both them!

Actually i disagree with this term..
Sometimes i know better than him/her that he is wrong, therefore any smart sells person should know when to say no to his client, always the psychologist has a nice term how they can heal their patients which says imagine the patient is walking in the snow you have to put your steps in the traces that he makes till you will reach the core of the problem then after he will follow you as a half blind person and you have to keep him following you all the way long during the healing process i would translate that in sale term Imagine the patient is your client you follow him to reach the core of his needs and help him there to arrange the priorities and let him follow you for the exact solutions for his needs Sometimes he will ask for some services he doesn't need here you will say you are mistaken you don't need that service because every human being has the tendency to teach and suggest and this is critical in the first selling you have to choose your words very carefully for telling him you are wrong in a polite way, so you will keep him behind you till the review will end.
and the buying - selling cycle will be closed..
don't forget whome has the money sets the rules but you can help him to set the rules for what he needs and the rules should fit the needs no more no less..
therefore he is not always right but he is always setting the rules..
I agree with this term

There is also another phrase that leads to the same meaning which is "Customer is a king" Both of them means that the customer should be the center of any action taken in the company and when there is conflict between the customer and the organization the customer perspective should be considered because all the employees in the organization are working towards one goal which is creating value for the customer.
This implies that whenever your customer has a complain or a weird request, red flags should be raised because this means that the value offered by your organization don't satisfy your customer and immediate revision for your value creation process should take place.
Frankly, whenever you receive a customer complain you should be grateful for him because he is offering you free consulting to continuously improve your business.
Thanks @Mohammad for your question and hope that my answer was helpful.