Voicing is whether the vocal folds vibrate or not. The sound /s/ is called voiceless because there is no vibration, and the sound /z/ is called voiced because the vocal folds do vibrate (you can feel on your neck if there is vibration.) Only three sounds in English have aspiration, the sounds /b/, /p/ and /t/.
An extra puff of air is pushed out when these sounds begin a word or stressed syllable. Hold a piece of paper close to your mouth when saying the words pin and spin. You should notice extra air when you say pin. Aspiration is indicated in writing with a superscript h, as in /pʰ/. Nasal sounds are produced when the velum (the soft palate located in the back of the roof of the mouth) is lowered and air is passed through the nose and mouth. Oral sounds are produced when the velum is raised and air passes only through the mouth.