Russia is a belligerent country. This country has invaded several other countries in the last 60 years. (Non-essential information)

The Titanic was the deadliest shipwreck in history. This ship sank due to excess of confidence and lack of attention. (Non-essential information)

Think about a DEFINING RELATIVE CLAUSE with the relative pronoun WHOM

Think about a NON-DEFINING RELATIVE CLAUSE with the pronoun WHEN

COVID has been forgotten by people. These people are not caring anymore. (Essential information)

Elon Musk bought Twitter. He is a billionaire. (Non-essential information)

The family will be visiting Canada. The winter finishes. (Essential information)

The economy of Colombia is rising. This economy was having a bad time. (Non-essential information)

Women are fighting for their rights and freedom. These rights were constrained along history (Essential information)

Laura is working on a tender. Her job is in Kingston. (Non-essential information)

Alexa is in love with Alea. Alea is a marvelous woman (Essential information)

Spain is a big country. In this place people are very kind. (Non-essential information)