Use the @pytest.mark.name decorator to tag the tests.

examples/pytest/test_by_marker.py
import pytest

@pytest.mark.smoke
def test_database_read():
    assert True

@pytest.mark.security
@pytest.mark.smoke
def test_database_write():
    assert True

@pytest.mark.security
def test_database_forget():
    assert True

@pytest.mark.smoke
def test_ui_access():
    assert True

@pytest.mark.security
def test_ui_forget():
    assert True

pytest --collect-only -m security test_by_marker.py
    test_ui_forget
    test_database_write
    test_database_forget
pytest --collect-only -m smoke test_by_marker.py
    test_database_read
    test_ui_access
    test_database_write