One school of thought is that brands should focus on penetration not loyalty, while others believe it is equally important - and recommend great brand building, positive brand experiences and strong consumer-brand relationships to build and retain it. A deep engagement strategy is one way to do this.
Brand loyalty can be viewed as behavioural and attitudinal. Behaviourally, it is sticking with a brand at purchase or purchasing it more often than competitors e.g. in FMCG where decisions are more frequent. It is commonly measured as the percentage of customers repeat purchasing or the percentage of share of customer category requirements. Attitudinally, it is preferring a particular brand to competitors. There are various measurement methods but most evaluate the depth of brand-customer relationships.