how is it used in modern times?
In most Commonwealth realms, the phrase does not appear in the Monarch's full style, though the initial "By the Grace of God" is maintained
Defender of the Faith
In most Commonwealth realms, the phrase does not appear in the Monarch's full style, though the initial "By the Grace of God" is maintained. 
when did the queen have her first child 14 November 1948 what are the titles she has? "Queen of Jamaica and her other realms and territories", "Queen of Australia and her other realms and territories", "Duke of Normandy and Lord of Mann", Defender of the Faith and Duke of Lancaster what does the second-last title mean? It reflects the Sovereign's position as the supreme governor of the Church of England, who is thus formally superior to the archbishop of Canterbury
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Defender of the Faith [SEP] Modern usage
The decision of the Royal Mint to omit this and certain other parts of the monarch's style from the "Godless Florin" in 1849 caused such a scandal that the coin was replaced. In most Commonwealth realms, the phrase does not appear in the Monarch's full style, though the initial "By the Grace of God" is maintained. For example, in Australia, Queen Elizabeth is currently styled "by the Grace of God, Queen of Australia and Her other Realms and Territories, Head of the Commonwealth". She is additionally styled "Defender of the Faith" only in Canada, New Zealand and the UK. Canada chose to include the phrase not because the sovereign is regarded as the protector of the state religion (Canada has none), but as a defender of faith in general.