Optional is a container object which may or may not contain a non-null value. If a value is present, isPresent() will return true and get() will return the value.
Additional methods that depend on the presence of the contained value are provided, such as orElse(), which returns a default value if value not present, and ifPresent() which executes a block of code if the value is present.
“ An optional value either contains a value or contains nil to indicate that a value is missing”
Excerpt From: Apple Inc. “The Swift Programming Language (Swift 3.1 Edition).” iBooks. https://itun.es/us/k5SW7.l
Basic optional use cases include: for a constant (let), use of an optional within a loop (if-let), safely unwrapping an optional value within a method (guard-let), and as part of switch loops (case-let), defaulting to a value if nil, using the coalesce operator (??)