Novo vs. jovem
In Portuguese, both novo and jovem can relate to the concept of youth or recentness, but they are not interchangeable. The main distinction lies in what they describe: novo primarily means new, while jovem specifically means young.
Novo
A1The word novo primarily means new. It is used for things that have recently been created, acquired, or started. While it can also mean young or younger, it often does so in the context of being at an early stage of its existence (like wine) or in direct age comparisons.
Eu comprei um carro novo.
(I bought a new car.)
Este é o meu novo endereço.
(This is my new address.)
Ela começou um capítulo novo na sua vida.
(She started a new chapter in her life.)
O meu irmão é mais novo do que eu.
(My brother is younger than me.)
Este queijo ainda é muito novo, precisa de mais tempo para curar.
(This cheese is still too young, it needs more time to cure.)
Desejo a todos um feliz Ano Novo.
(I wish everyone a happy New Year.)
Jovem
A2The word jovem specifically means young. It almost exclusively describes a person or another living being in an early stage of life, typically between childhood and middle age. It refers to the quality or state of being young, not just newness.
Aquele ator é muito jovem e talentoso.
(That actor is very young and talented.)
O festival de música atrai muitos jovens.
(The music festival attracts many young people.)
Ela é uma médica jovem, mas muito competente.
(She is a young doctor, but very competent.)
O meu avô tem 90 anos, mas tem um espírito jovem.
(My grandfather is 90 years old, but he has a young spirit.)
O filhote de leão ainda é muito jovem para caçar sozinho.
(The lion cub is still too young to hunt alone.)
A empresa procura contratar uma equipa jovem e dinâmica.
(The company is looking to hire a young and dynamic team.)
Summary
In short, use novo for things that are new (like a car, a house, or an idea) or to say someone is younger than another. Use jovem to describe a person or living being as young in age or spirit. You can have a carro novo (new car), but not a carro jovem (young car). While you can call a person novo in some contexts (like being new to a job), jovem is the correct and most common word to describe them as young.