Some legal terms carry their own peculiar definition but others mean exactly what they seem to mean. The expression share and share alike means the same thing in a will that it does on the playground: everyone who is included in the group at the time of distribution gets an equal share of the object or assets in question.
A will is a legal document in which a person describes who she wants to have her assets when she dies. Bequests in a will can leave all property to one specified person or you may divide assets between two or more individuals. If an item such as a ring or a car is left in equal shares to more than one person, it is generally sold and the proceeds are divided equally.
When the person making a will wants two or more persons to have equal shares in an asset or in the entire estate, she can use the term "share and share alike." For example, a will-maker might leave a bank account to "my three daughters, share and share alike." This indicates that each of the daughters gets one-third of the money in the account. If one daughter dies before the person who created the will, in most jurisdictions the two remaining daughters will split the money.